Exhibit 99.1

MarkWest Energy Partners Closes Public Offering
of $300 Million of 6.5% Senior Notes Due 2021

DENVER—February 24, 2011—MarkWest Energy Partners, L.P. (NYSE: MWE and the “Partnership”) and its subsidiary MarkWest Energy Finance Corporation announced today the closing of a public offering of $300,000,000 of 6.5% senior unsecured notes due 2021 (the “Notes”) at par.

The Partnership intends to use the net proceeds from the Notes offering to purchase later today $272,205,000 aggregate principal amount of its 8.5% senior notes due 2016 (CUSIP Nos. 570506AE5 and 570506AD7) that have been tendered and accepted for purchase pursuant to a tender offer for any and all of such outstanding notes.

Barclays Capital acted as sole book-running manager for the Notes offering. A copy of the prospectus supplement and accompanying base prospectus associated with this offering may be obtained from the underwriter as follows:

Barclays Capital

c/o Broadridge Financial Solutions

1155 Long Island Ave.

Edgewood, NY 11717

barclaysprospectus@broadridge.com

Toll-Free: (888) 603-5847

An electronic copy of the prospectus supplement and the accompanying base prospectus is available from the Securities and Exchange Commission’s (SEC) web site at http://www.sec.gov. The Notes were offered pursuant to an effective shelf registration statement that the Partnership previously filed with the SEC. This press release shall not constitute an offer to sell or the solicitation of an offer to buy nor shall there be any sale of these Notes in any state in which such offer, solicitation, or sale would be unlawful prior to registration or qualification under the securities laws of such state.

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MarkWest Energy Partners, L.P. is a master limited partnership engaged in the gathering, transportation, and processing of natural gas; the transportation, fractionation, marketing, and storage of natural gas liquids; and the gathering and transportation of crude oil. MarkWest has extensive natural gas gathering, processing, and transmission operations in the southwest, Gulf Coast, and northeast regions of the United States, including the Marcellus Shale, and is the largest natural gas processor and fractionator in the Appalachian region.

This press release includes “forward-looking statements.”  All statements other than statements of historical facts included or incorporated herein may constitute forward-looking statements.  Actual results could vary significantly from those expressed or implied in such statements and are subject to a number of risks and uncertainties.  Although we believe that the expectations reflected in the forward-looking statements are reasonable, we can give no assurance that such expectations will prove to be

correct.  The forward-looking statements involve risks and uncertainties that affect our operations, financial performance, and other factors as discussed in our filings with the Securities and Exchange Commission.  Among the factors that could cause results to differ materially are those risks discussed in the periodic reports we file with the SEC, including our Annual Report on Form 10-K for the year ended December 31, 2009, and our Quarterly Report on Form 10-Q for the quarter ended September 30, 2010.  You are urged to carefully review and consider the cautionary statements and other disclosures made in those filings, specifically those under the heading “Risk Factors.”  We do not undertake any duty to update any forward-looking statement except as required by law.